Synthesis and Photovoltaic Properties of Copolymers from Benzodithiophene and Thiazole

Two new D-A conjugated polymers containing a benzodithiophene donor unit and the acceptor unit of bithiazole (BTz) or thiazolothiazole (TzTz). P1 and P2, were synthesized by Stille cross-coupling polymerization. The thermal, optical, and electrochemical properties were well investigated. Bulk heterojunction polymer solar cell devices based on an active layer of electron donor copolymers. P1 and P2 blended with electron acceptor [6,6]-phenyl-C-71 butyric acid methyl ester (PC71BM) in a weight ratio of 1:2 were explored; the external quantum efficiency (EQE) measurements showed a peak external quantum efficiency of 45% for P1 and P2. The first result or the PSC device with P2 and PC71BM in a weight ratio or 1:2 gave an overall power conversion efficiency (PCE) of 2.6%, an open-circuit voltage of 0.77 V, a short-circuit current of 6.68 in A/cm(2), and a fill factor of 0.51, under the illumination of AM1.5, 100 mW/cm(2).